Once you have mapped UVs onto a model you view and edit the resulting UV texture coordinates using the UV Texture Editor. The UV Texture Editor lets you view the two-dimensional UV mesh on its own or in relation to the image texture. The UV Texture Editor lets you manipulate the components of the UV mesh in the 2D view much like you work with other polygon components in Maya.

In some instances the default UV projection may not appear in a manner you expect or require. In these situations you must visually evaluate, then manually edit the UV layout to rearrange the position of the UVs within the UV Texture Editor to better suit the requirements of the texture.

In terms of production workflow, you typically map and edit (rearrange) the UVs once you have completed your modeling and before you assign textures to the model. How you edit the UVs for a particular polygon mesh depends on the texture mapping requirements you have.

The following are some examples of situations where UVs need to be edited to meet specific texturing requirements.

• When the image for a texture map already exists, the UV mesh (and possibly the surface mesh) will need to be modified to conform to the requirements of the image. One example of this is when texture mapping a games character and the artwork for the texture maps already exist for a known film actor, athlete, or comic book character. In addition, the image for the character's textures may be comprised of many smaller separate images for the various components of the character on the same image (For example, sub-images of the face or head, torso, legs etc.). This method of laying out many images on a single image is commonly referred to as a decal sheet and is very efficient in terms of texture and memory usage for an interactive game application. When using a decal sheet approach the UVs must be arranged so they match up with the corresponding images on texture map as it appears in the UV Texture Editor.
• When you want to reference the same image multiple times for a texture map you will want the UVs to lay directly on top of each other when viewed in the UV Texture Editor. This approach is useful and efficient in situations when the UVs can share the same region of a texture image. For example, if you had a brick texture that you wanted repeated on several buildings in a scene you could lay each separate UV mesh in exactly the same position within the UV Texture Editor. Otherwise overlapping UVs are generally not desirable and will produce unexpected texture mapping results. When UVs overlap you can lay them out to not overlap using Edit UVs > Layout.
• When you need to manually reassemble a UV mesh after using Automatic mapping to create UVs for a surface mesh. Automatic mapping invariably produces multiple projections for a surface mesh based on the shape of the surface mesh. As a result, the UV projections appear as many separate UV components in the UV Texture Editor. This can be problematic when you need to have a UV mesh that is one contiguous piece to allow a texture artist to paint directly on the 3D object. You can reposition and attach the individual UV components using features in the UV Texture Editor such as Polygons > Move and Sew UV Edges.
• When the shape of the projected UVs are badly distorted compared to the 3D surface mesh the resulting texture map will be compressed, stretched or otherwise distorted on the surface mesh in an undesirable fashion. There are many options for correcting these situations using features in the UV Texture Editor such features as Unfold and Relax.
  Note

  To create a UV mapping arrangement that works best for your model, you may need to try a variety of mapping techniques, until you find a mapping arrangement that is suitable. For more information on laying out UVs see UV mapping tips.